This invention relates to the synthesis of an reaction rates at high yields via the disclosed use of solvent, phase separation, and recycle of EO, solvent and other components. One or more liquid-liquid phase separations/extractions prior to thermal recovery of product 1,3-PDO optimizes the use of valuable hydroformylation catalysts.
Aliphatic 1,3-diols, particularly 1,3-propanediol, have many applications as monomer units for polyester and polyurethane, and as starting materials for the synthesis of cyclic compounds. For example, CORTERRA(copyright) polymer is a polyester characterized by outstanding properties that is made of 1,3-propanediol (hereafter 1,3-PDO) and terephthalic acid. There is much interest in the art in finding new routes for synthesizing 1,3-PDO that are efficient, economical, and demonstrate process advantages.
U. S. Pat. Nos. 3,463,819 and 3,456,017 teach the hydroformylation of ethylene oxide to produce 1,3-propanediol and 3-hydroxypropanal (hereafter 3-HPA) using a tertiary phosphine-modified cobalt carbonyl catalyst. U.S. Pat. No. 3,687,981 discloses a process for synthesizing 1,3-PDO. In this process phase separation of intermediate product hydroxyethyl hydroxy dioxane occurs at room temperature, or cooler, before the material goes on to hydrogenation to product. U.S. Pat. Nos. 5,256,827; 5,344,993; 5,459,299; 5,463,144; 5,463,145; 5,463,146; 5,545,765; 5,545,766; 5,545,767; and, 5,563,302, 5,689,016, all assigned to Shell, disclose cobalt catalyzed hydroformylation of ethylene oxide.
U.S. Pat. No. 5,304,691, assigned to Shell, discloses a method of hydroformylating ethylene oxide to 3-hydroxypropanal and 1,3-propanediol in a single step using an improved catalyst system comprising a cobalt-tertiary phosphine ligand in combination with a ruthenium catalyst. In ""691 1,3-PDO and 3-HPA are produced by intimately contacting an oxirane, particularly ethylene oxide (EO), a ditertiary phosphine-modified cobalt carbonyl catalyst, a ruthenium catalyst promoter, and syngas (carbon monoxide and hydrogen) in an inert reaction solvent at hydroformylation reaction conditions. A PDO yield of up to 86-87 mole % is reported, using a catalyst comprising cobalt ligated with 1,2-bis (9-phosphabicyclononyl) ethane as bidentate ligand, and either triruthenium (0) dodecacarbonyl or bis[ruthenium tricarbonyl dichloride] as cocatalyst. Also see U.S. Pat. No. 5,304,686, assigned to Shell, which discloses the synthesis of 3-hydroxypropanal using a ditertiary phospine-modified cobalt carbonyl catalyst and a catalyst promoter.
Copending U.S. patent application Ser. Nos. 09/808,974, filed Mar. 15, 2001; Ser. No. 60/291,826, filed May 18, 2001; Ser. No. 60/295,769, filed Jun. 4, 2001; and Ser. No. 60/291,827, filed May 18, 2001, all incorporated herein by reference in the entirety disclose ligated bimetallic catalyst compositions useful in the one step synthesis of 1,3-PDO, and methods for the manufacture thereof.
It would constitute a distinct advance in the art if there were a single-step process for synthesizing 1,3-PDO which could be run as a single phase with sufficient concentration of 1,3-PDO such that upon cooling phase separation could be invoked by temperature reduction, removal of a miscibilizing solvent, and/or addition of a phase split-inducing agent; and the product PDO could be separated from the reaction solvent without the use of high cost extraction or distillation methods, thus permitting valuable hydroformylation catalyst to be recycled without degradation or exposure to downstream processing. Furthermore, it would be extremely efficient, and allow greater flexibility in processing, if residual EO in the crude PDO product could be converted using the product itself as the solvent, and if heavy ends could be purged from the system with minimal impact to the catalyst.
In accordance with the foregoing, the present invention is a process for synthesizing 1,3-PDO in one step in high yields at commercially viable reaction rates, where recovery of product is preferably accomplished via phase separation of a diol rich phase from the bulk reaction liquor, which comprises the steps of:
(a) Contacting, in a reaction vessel, ethylene oxide, carbon monoxide, hydrogen, a non-water-miscible solvent, and a homogeneous bimetallic hydroformylation catalyst comprising an essentially non-ligated cobalt carbonyl compound and a second Group VIII metal component, preferably selected from the ruthenium or iron, optionally ligated with a ligand selected from a phosphine ligand, a bidentate or multidentate N-heterocyclic ligand, a porphorine ligand; or a phospholanoalkane ligand;
(b) Heating said mixture to a temperature within the range from 30 to about 150xc2x0 C. and a pressure within the range of about 100 to about 4000 psig for a time effective to produce a single-phase reaction product mixture containing sufficient concentration of 1,3-PDO such that phase separation can be invoked by temperature reduction to result in a phase comprising a major portion of the solvent, at least about 50 wt % of the catalyst composition, plus unreacted ethylene oxide, and a second phase, which comprises a major portion of 1,3-propanediol, a small portion of catalyst, solvent, and heavy ends;
(c) Optionally, instead of or in addition to temperature reduction, inducing phase separation by at least one method selected from removing miscibilizing solvent, or adding a phase split-inducing reagent;
(d) Optionally allowing a two-phase reaction mixture to form during reaction step (b);
(e) Separating said two-phase reaction mixture;
(f) Recycling the phase rich in solvent, catalyst, and unreacted EO, directly to the hydroformylation reaction for further reaction with previously unreacted starting materials;
(g) Directing the second phase to a thermal recovery unit where solvent and catalyst are recycled back to step (a), 1,3-PDO is recovered, and heavy ends are purged.
The present invention is a novel process for synthesizing 1,3-PDO in one-step, which enables operations at commercially viable reaction rates at high yields. At a target 1,3-PDO concentration, the reaction mixture partitions into a predominately solvent phase and a predominately 1,3-PDO phase from which 1,3-PDO can be readily recovered. Crude product PDO separation from the solvent is enabled either during or downstream of reaction via a method selected from temperature reduction, removal of miscibilizing solvent, or addition of a phase split-inducing reagent. PDO product recovery, recycle of residual catalyst, and removal of heavy ends are accomplished primarily through distillation and/or extraction processing.